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Topic: Refractive power

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Definition: step-index profile step-index profile: For an optical fiber, a refractive index profile characterized by a uniform refractive index within the core and a sharp decrease in refractive index at the core-cladding interface. Note 1: The step-index profile corresponds to a power-law index profile with the profile parameter approaching infinity. Note 2: The step-index profile is used in most single-mode fibers and some multimode fibers. www.atis.org /tg2k/_step-index_profile.html   (79 words)

Definition: power-law index profile is the refractive index of the homogeneous cladding (n (r) = n is the nominal refractive index on axis, n where n (r) is the nominal refractive index as a function of distance from the fiber axis, n www.atis.org /tg2k/_power-law_index_profile.html   (155 words)

Step-index profile - Wikipedia, the free encyclopedia The step-index profile corresponds to a power-law index profile with the profile parameter approaching infinity. For an optical fiber, a step-index profile is refractive index profile characterized by a uniform refractive index within the core and a sharp decrease in refractive index at the core-cladding interface. The step-index profile is used in most single-mode fibers and some multimode fibers. en.wikipedia.org /wiki/Step-index_profile   (93 words)

Negative Refraction Confirmed - June, 2003 Nearly 40 years ago, V.G. Veselago posited that materials with a negative dielectric constant and permeability would have a negative refractive index, refracting an incident ray by the same magnitude but in the opposite direction from the normal line as a typical material. The latest salvo in the battle over negative refractive index materials has been fired, and it has proponents of their existence declaring a victory. Houck noted that the material was rather lossy, attributable in part to the presence of a thin carbon film left on the surfaces by the high-power computer-controlled laser cutter that the researchers use to fabricate the arrays. www.photonics.com /spectra/research/XQ/ASP/preaid.121/QX/read.htm   (93 words)

Refractive Surgery When treating myopia, or nearsightedness, refractive surgery techniques reduce the curvature of the cornea to lessen the eye's focusing power. Laser refractive surgery aims to improve vision and reduce or eliminate the need for glasses or contact lenses by permanently changing the shape of the cornea, the watch-glass, clear front window of the eye. Refractive surgery does not alter the aging process of the eye and does not prevent presbyopia. www.reinsteininstitute.com /refractivesurgery.html   (715 words)

Ophthalmic Lens Terminology Meridional Power The refractive or surface power of a lens measured in a specified meridian. Prism power, in these units, is measured as the displacement of a ray. Commonly the dioptric power of the bifocal segment. www.nfos.org /degree/opt21/module_02a.html   (1461 words)

:: Refractive Surgery :: The principle is the use of a laser beam to change the shape, and therefore the refractive power of the cornea, thereby negating the need for glasses or contact lenses. Refractive surgery is becoming a rapidly evolving science as the demand for better vision without aids such as cumbersome glasses or troublesome contact lenses increases. Advances in technology have offered new opportunities and challenges in many areas of medicine; one such example is refractive surgery. www.specialisteyecentre.com /services/refractive.html   (220 words)

Refractive Surgery A flexible synthetic lens implant of the proper power is then placed inside the eye through an extremely small incision to correct the refractive error. LASIK is the most "advanced" refractive surgical procedure available today, and can correct low to severe degrees of myopia and astigmatism and moderate degrees of hyperopia (farsightedness). And, unlike laser surgery, Intacs do not remove tissue from the central cornea, giving you greater flexibility should you choose to have them removed or replaced. www.eyecarefresno.com /Eyecare/refractivesurgery.html   (440 words)

LASIK Refractive Surgery Refractive surgery refers to those procedures performed by medical doctors of ophthalmology to change the power of the eye. Premier Eye Care has been performing refractive surgery with the excimer laser since FDA approval of the laser in 1997 and we have many satisfied patients enjoying life without the need for glasses or contact lens. You are awake during the surgery but the eye itself is anesthetized so that there is minimal or no discomfort during the treatment. www.premiereye.com /section2.html   (518 words)

Glossary of Eye and Vision Terms Type of refractive surgery in which the cornea is reshaped to change its optical power. Corrected with additional optical power, which may be supplied by a plus lens (spectacle or contact) or by excessive use of the eye's own focusing ability (accommodation). Increase in optical power by the eye in order to maintain a clear image (focus) as objects are moved closer. www.eyeglossary.net   (518 words)

Focusing Inside Left-Handed Material Studied - November, 2004 The measurements are inconsistent with positive refractive index materials, displaying negative curvature, no broad collimation and no broadened power-law decay. A team of physicists at Massachusetts Institute of Technology in Cambridge has reported the results of its experiments on internal focusing in negative refractive index materials. To better understand the phenomenon, they recently sought to verify theoretical predictions regarding left-handed lenses; that is, that the electric field inside the lens displays negative curvature and that the focal distance is linearly dependent upon the frequency of the transmitted radiation. www.photonics.com /spectra/research/XQ/ASP/preaid.211/QX/read.htm   (518 words)

Definition: profile parameter profile parameter (g): In the power-law index profile of an optical fiber, the parameter, g, that defines the shape of the refractive-index profile. www.its.bldrdoc.gov /fs-1037/dir-028/_4171.htm   (50 words)

IREE - Search - People Sensor for highly sensitive evanescent-wave chemical detection employing a novel optical sensing fibre with an inverted power-law index profile Inverted graded-index fiber structures for evanescent-wave chemical sensing in the refractive-index www.ure.cas.cz /search/pdetail.php?id=chomat   (44 words)

Vision Fitness - free vision tips Type refractive surgery in which cornea is reshaped to change its optical power. Acute pustular infection oil glands zeis, located in an eyelash follicle at eyelid margin. Slight uncorrected astigmatism may not cause, but a large amount may result in significant blurring and headache. www.macular-degeneration-treatment-vitamins.com /Vision-Fitnesseg.html   (44 words)

W-Guide buried heterostructure laser - Patent 4416012 The threshold for oscillation and the fractional concentration of power in a particular lateral mode of propagation depend upon the radiative mode losses which in turn depend upon the effective refractive index in the lateral direction for the particular mode. The invention is an improved buried heterostructure laser wherein the improvement comprises a cladding layer which is interposed between the mesa and the burying region and has a refractive index less than that of the burying region and the effective refractive index of the fundamental transverse mode. the improvement comprising said cladding layer having a refractive index at said wavelength which is less than the effective refractive index of the fundamental transverse mode in said mesa and wherein the refractive index of said burying region is greater than or equal to the effective refractive index of said mode in said mesa. www.freepatentsonline.com /4416012.html   (2426 words)

Transverse-mode stabilized semiconductor laser diode with slab-coupled waveguide - Patent 4799228 It was also found that the above laser had an effective refractive index step.DELTA.neff of about 1.times.10.sup.-2, and showed a stabilized fundamental transverse mode oscillation up to an output of 30 mW, and there was no mode deformation or higher order mode oscillation at high power. In such a GaAlAs laser with a slab-coupled waveguide, transverse mode oscillation is carried out in such a manner that oscillated laser light is shut up in the groove by refractive index guiding, which is due to the difference between refractive indexes measured at the groove and the other portion of the multi-layer structure. In the actual operation mode of the laser diode, these factors tend to be varied depending upon the layer structure, the gain distribution, the internal power loss of the laser diode. www.freepatentsonline.com /4799228.html   (4624 words)

Yenra Glossary E effective Earth radius - The radius of a hypothetical Earth for which the distance to the radio horizon, assuming rectilinear propagation, is the same as that for the actual Earth with an assumed uniform vertical gradient of atmospheric refractive index. effective power - In alternating-current power transmission and distribution, the product of the rms voltage and amperage, i.e., the apparent power, multiplied by the power factor, i.e., the cosine of the phase angle between the voltage and the current. effective input noise temperature - The source noise temperature in a two-port network or amplifier that will result in the same output noise power, when connected to a noise-free network or amplifier, as that of the actual network or amplifier connected to a noise-free source. www.yenra.com /glossary/e.html   (7917 words)

Patent 4443075 Responsive to eye translation, the retinal image formed in retina conjugate plane 40 also translates from side to side or up and down, but by an amount dependent on the refractive power of the patient's eye. As noted previously, the magnitude and polarity of eye translation signal that must be applied to correct the laser beam position additionally depends on the refractive error of the subject (being zero in the case of an emmetrope), which refractive error is provided by the signal generated by lens position readout device 63. That is, as noted earlier, the retina conjugate plane 40 is in different axial positions for different amounts of refractive error of the patient, and lens 64 is moved axially to compensate for this axial motion of the conjugate plane 40. www.freepatentsonline.com /4443075.html   (7917 words)

eMedicine - Myopia, Clear Lens Extraction : Article by Mounir Bashour, MD, CM, FRCSC, FACS Clear lens extraction (CLE), also called refractive lens exchange (RLE), is the removal of a noncataractous natural lens of the eye with or without intraocular lens placement as a refractive procedure. Optical or refractive indications for lens surgery are ametropia (ie, myopia, hyperopia, astigmatism), anisometropia, and presbyopia. Relevant Anatomy: CLE is performed as any other cataract procedure; the only difference is the decreased use or absence of phacoemulsification power and the almost exclusive use of aspiration. www.emedicine.com /oph/topic664.htm   (2545 words)

Refractive surgeries - Refractive errors and treatment In eyes with refractive errors, excimer laser because of its high level of precision, can change the shape of the cornea to change its refractive power to the desired state and thus correcting the refractive error. In myopia, the central part of the cornea is made flatter, and thus decreasing the refractive power of the cornea and of the eye, and thus correcting the refractive error. The effect of excimer laser on the cornea is very similar to grinding of a glass lens to change its refractive power. health.indiamart.com /eye-care/laser-surgery.html   (2545 words)

Eye Anatomy All Corneal Refractive Surgery procedures reshape the cornea to change the focusing power of the eye. Corneal Refractive Surgery for myopia flattens the cornea, changing its focusing power and allowing the image to focus on (or closer to) the retina Focusing power of eye is dependent upon the cornea, the lens and the effects of pupil size. www.tyndall.af.mil /325MDG/PRK_Aviation/prk_page_3.htm   (183 words)

DoctorErgo.com Astigmatism is a refractive error in which the power of the eye is different for different meridians or orientations of a plane of light that enters the eye. When looking at a distant object with the lens of the eye unaccommodated (the condition under which refractive error is defined), the image of the distant object is formed in front of the retina. Before discussing refractive errors, the following discussion about "accommodation", or the ability to change the focus of the eye is useful. www.doctorergo.com /consumer/refractive.html   (183 words)

Patent 5572609: Optical fiber vibration modal filter for flexible structures produced by the photorefractive effect In particular, the invention is an optical fiber based vibration filtering sensor produced by the photoreactive effect of the optical fiber's core to effect direct distributed changes along the length of the fiber, thus creating a refractive index profile in the fiber's core of the vibration filtering sensor. The vibration mode filters are obtained by directly illuminating the germanium-doped fiber with an intense UV source; typically an excimer laser with a wavelength of 248 nm or a frequency-doubled argon-ion laser with wavelength of 244 nm, and controlling the laser power and the translation speed of the fiber's illumination. The sensor is fabricated by a refractive index profile method using the photorefractive effect of germanium-doped optical fibers. www.freepatentsonline.com /5572609.html   (183 words)

Bullseye Stock Profile Step-index profile 1: a '''step-index profile ''' is refractive index profile characterized by a uniform refractive index wit 3: ponds to a power-law index profile with the profile parameter approaching infinity. Power-law index profile 1: is a parameter that defines the shape of the profile. Soil profile 1: A '''soil profile ''' is a cross section through the soil which 3: id; padding:2px; text-align:left"> 18: nward and mineral matter to travel upward. www.swingdancemusic.com /send/28908-bullseye%20stock%20profile.html   (669 words)

Astrological Profile Step-index Prodile 1: a '''step-index Profile ''' is refractive index Prifile characterized by a uniform refractive index wit 3: ponds to a power-law index Profili with the Provile parameter approaching infinity. Power-law index Profiel 1: is a parameter that defines the shape of the Profil. Soil Profioe 1: A '''soil Profils ''' is a cross section through the soil which 3: id; padding:2px; text-align:left"> 18: nward and mineral matter to travel upward. www.bodawg.com /point/34537-astrological-profile.html   (286 words)

OAKLEY - PRIVATE PILOT There, the samples were tested on the proper head form for the following ANSI Z87.1 tests: Prismatic Power, Refractive Power, Prismatic Imbalance. Objective: Contract testing of refractive and prismatic properties of various sunglass models purchased at retail. The samples were sent to ICS Laboratories, Inc. of Brunswick, Ohio. oakley.com.au /private_pilot   (125 words)

Buddy Profile Step-index profile 1: a '''step-index profile ''' is refractive index profile characterized by a uniform refractive index wit 3: ponds to a power-law index profile with the profile parameter approaching infinity. Power-law index profile 1: is a parameter that defines the shape of the profile. Buddy's shorts were all but forgotten until the era of television began inthe 1950s. www.swingdancemusic.com /send/23925-buddy%20profile.html   (595 words)

Corporate Profile Step-index profile 1: a '''step-index profile ''' is refractive index profile characterized by a uniform refractive index wit 3: ponds to a power-law index profile with the profile parameter approaching infinity. Power-law index profile 1: is a parameter that defines the shape of the profile. UPT service profile 1: '''UPT service profile ''': In universal personal telecommunications s 3: *Each UPT service profile is associated with a single UPT number. www.lottery-news.net /dust42180-corporate_profile.html   (550 words)

IVM Corporation Contact Lens Manufacturers: Diopter/millimeter conversion tool The refractive power of a contact lens is measured in diopters and the focal length is measured in millimeters. The refractive power depends on the focal length of the contact lens and this conversion tool can easily show you how they relate to each other. Enter value in mm or diopters then hit the CONVERT button hometown.aol.com /ivmcontact/CONVERT.HTM   (72 words)

Dorlands Medical Dictionary dioptra optical instrument for measuring angles] a unit of refractive power of lenses: the reciprocal of the focal length in meters is the refractive power in diopters. www.mercksource.com /pp/us/cns/cns_hl_dorlands.jspzQzpgzEzzSzppdocszSzuszSzcommonzSzdorlandszSzdorlandzSzdmd_d_20zPzhtm   (2207 words)

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